PRACTICAL ORGANIC CHEMISTRY
This forms chlorocaffeine, which is then reduced with hydriodic
acid to caffeine,
The same result may be obtained in a simpler way by
nethylating uric acid, and converting it into trimethyluric acid
and then into caffeine ; or by preparing the mono- and cli-mcthyl
derivatives of uric acid, reducing these to the corresponding
mono- and di-methylxanthines and introducing additional
methyl groups into the product.
Tyrosine, Leucine.—It has long been known that mineral
acids and alkalis possess the property of breaking up albuminoid
substances and resolving them into the simpler ami no-acids.
The recent introduction by Fischer of a method of separating
the amino-acids by converting them into volatile esters followed
by fractional distillation in vacuo has led to the recognition of the
wide distribution of such acids as alanine, serine, and phcnyl-
alanine, and to the discovery of two cyclic acids, pyrrol idine-
carboxylic acid and hydroxypyrrolidine carboxylic acid. The
following is a list of amino-acids from albuminoid substances
which have been separated by fractional distillation of their
esters under reduced pressure :
Pressure in rnm.
Glycocoll . , .
tl 'p — CO'C0
Alanine ....... Aminoisovaleric acid . Leucine ....... Aspartic acid
JL j j~ :>
Glutamic acid ..... Phenylalanine .....
139 — 140° 143°